Lots of players this year (I'm looking at Garrigues at the moment, but Melzer was another) are sporting flourescent yellow shirts.
Obviously that must cause the opponent to lose their fix on the ball once in a while, particularly when both are at the net and the yellow fills a larger part of the opponent's visual field.

Rationale of the yellow balls is visibility, and this defeats that purpose, deliberately and cynically I suspect. Seems to be a case where a rule has become necessary.

Shouldn't be allowed to wear blue either. Clearly an attempt to blend in with the court surface.

Heh, just watching Tsonga-Blake, where Tsonga wears yellow shirt of almost same colour as the ball, and Blake wears blue shirt, almost same colour as the court

I've been wondering sometimes why the players won't take advantage of "camouflage colours", but I guess they do now? Blake kinda ruins the effect with his black shorts though - with his upper body blending with the court almost perfectly, it looks like there are pair of shorts running around...

edit: and Tsonga has also yellow shoes and yellow wristbands! He's really going all the way, and it seems to be working

"If Kafelnikov said that, he is right. Kafelnikov is always right."-Marat Safin